The present invention relates to battery cooling systems and, more specifically, to systems for cooling batteries for cordless power tools.
Cordless products which use rechargeable batteries are prevalent throughout the workplace as well as in the home. From housewares to power tools, rechargeable batteries are used in numerous devices. Ordinarily, nickel-cadium or nickelmetal-hydride battery cells are used in these devices. Since the devices use a plurality of battery cells, the battery cells are ordinarily packaged as battery packs. These battery packs couple with the cordless devices and secure to the device. The battery pack may be removed from the cordless device and charged in a battery charger or charged in the cordless device itself.
As the cordless power device is used, current flows through the batteries to power the cordless device. As current is drawn off the batteries, heat is generated within the battery pack. Also, during charging of the battery pack, heat is likewise accumulated during the charging process. The heat created during discharge of the batteries as well as charging of the batteries which, in turn, leads to increased temperatures, may have a severe effect on the life expectancy and performance of the batteries. In order for batteries to properly charge, the batteries must be below a desired threshold temperature and the differential temperature between the cells in the battery pack should be minimized. Likewise, if the batteries become too hot during use, battery life will be cut short. Also, if a battery is below a certain threshold temperature, it will be too cold to charge and must be warmed before charging. Thus, it is desirous to maintain batteries within a desired temperature range for optimum performance as well as optimum charging.
Further, battery packs typically contain some battery cells close to the outer walls of the pack, while some battery cells are surrounded by other battery cells. Those cells close to the outer walls have better thermal conductivity to the outside ambient than do the cells that are surrounded by other cells. When a battery pack is discharging on the cordless device, the amount of heat generated is approximately the same in each cell. However, depending on the thermal path to ambient, different cells will reach different temperatures. Further, for the same reasons, different cells reach different temperatures during the charging process. Accordingly, if one cell is at an increased temperature with respect to the other cells, its charge or discharge efficiency will be different, and, therefore, it may charge or discharge faster than the other cells. This will lead to a decline in the performance of the entire pack.
The present invention provides the art with a battery pack which dissipates heat within the battery pack during charging of the cells as well as discharging of the cells while the battery pack is in use.
In accordance with a first aspect of the invention, a cordless power tool to reduce charging time comprises a housing including a mechanism to couple a removable battery pack. A removable battery pack has a housing with one or more cells in the housing. A vent system is in the housing to enable fluid passage through the housing. A mechanism is associated with the battery pack to dissipate heat in the battery pack housing. This heat removal from the battery pack reduces the battery pack charging time. The heat dissipating mechanism may include fluid directors to move fluid around cells as desired. Also, alternatively, a heat sink may be used to dissipate heat from the cells. Further, alternatively, a fan may be used to force fluid through the vent system to dissipate heat from the battery pack. The fan may be either in the tool housing or in the battery pack.
In accordance with a second aspect of the invention, a cordless power tool to reduce charging time comprises a housing including a mechanism to couple with a removable battery pack. A removable battery pack has a housing with one or more cells in the housing. A vent system is in the housing to enable fluid passage through the housing. A mechanism is associated with the battery pack to dissipate heat from the battery pack. This heat removal from the battery pack reduces the battery pack charging time. The heat dissipating mechanism may include fluid directors to move fluid around the cells with higher temperatures. Further, alternatively, a heat sink may be used to dissipate heat from the cells. Also, alternatively, a fan may be used to force fluid through the vent system to dissipate heat from the battery pack. The fan may be either in the tool housing or in the battery pack. A battery charger to charge the battery pack is also included. The battery charger has a mechanism to move fluid through the vent system of the battery pack housing. The charger may include a fan to force air through the battery pack vent system. Further, the battery pack may include a fan and in this case the charger may include a vent system to enable fluid to pass by the cell or cells in the battery pack housing.
In accordance with a third aspect of the invention, a cordless power tool to reduce charging time comprises a housing including a mechanism to couple with a removable battery pack. A removable battery pack has a housing with one or more cells in the housing. A vent system is in the housing to enable fluid passage through the housing. A mechanism is associated with the battery pack to dissipate heat from the battery pack. This heat removal from the battery pack reduces the battery pack charging time. The heat dissipating mechanism may include fluid directors to move fluid around the battery cells. Also, alternatively, a heat sink may be used to dissipate heat from the battery cells. Further, alternatively, a fan may be used to force fluid through the vent system to dissipate heat from the battery pack. The fan may be either in the tool housing or in the battery pack. Also, a battery charger to charge the battery pack is included. Here, an auxiliary fan is coupled with the charger or battery pack to force air through the charger or battery pack vent systems. The auxiliary fan is capable of moving fluid through the battery pack while the battery pack is secured with the charger.
In accordance with a fourth aspect of the invention, a cordless power tool to reduce charging time comprises a housing including a mechanism to couple with removable battery pack. A removable battery pack has a housing with one or more cells in the housing. A vent system is in the housing to enable fluid passage through the housing. A mechanism is associated with the battery pack to dissipate heat from the battery pack housing. This heat removal from the battery pack reduces the battery pack charging time. The heat dissipating mechanism may include fluid directors to move fluid around the battery cells. Also, alternatively, a heat sink may be used to dissipate heat from the battery cells. Further, alternatively, a fan may be used to force fluid through the vent system to dissipate heat from the battery pack. The fan may be either in the tool housing or in the battery pack. A heat pump is included to provide heating or cooling of the battery cells depending upon the temperature of the battery cells. Thus, the heat pump enables the battery cells to be cooled if they are above a desired temperature and to be heated if the cells are below a desired temperature to enable charging of the cells.
In accordance with a fifth aspect of the invention, a cordless power tool to reduce charging time comprises a housing including a mechanism to couple with a removable battery pack. A removable battery pack has a housing with a plurality of cells in the housing. A vent system is in the housing to enable fluid passage through the housing. A mechanism is associated with the battery pack to dissipate heat or equalize temperatures in the battery pack. The heat removal from the battery pack reduces the battery pack charging time. The heat dissipating mechanism may include fluid directors to move fluid around the cells with higher temperatures. Also, alternatively, a heat sink may be used to dissipate heat from the higher temperature cells. Further, alternatively, a fan may be used to force fluid through the vent system to dissipate heat from the battery pack. The fan may be either in the tool housing or in the battery pack. A sensing mechanism may be included to sense the temperature of the plurality of cells in the battery pack housing. The heat dissipator equalizes the temperature of the plurality of cells. The heat dissipator wicks heat from the hotter cells to ambient or to the other cells to equalize cell temperature within the housing.
In accordance with a sixth aspect of the invention, a removable battery pack has a housing with one or more cells in the housing. A vent system is in the housing to enable fluid passage through the housing. A mechanism is associated with the battery pack to dissipate heat from the battery pack. This heat removal from the battery pack reduces the battery pack charging time. The heat dissipating mechanism may include fluid directors to move fluid around cells. Also, alternatively, a heat sink may be used to dissipate heat from the cells. Further, alternatively, a fan may be used to force fluid through the vent system to dissipate heat from the battery pack. The fan may be either in the tool housing or in the battery pack.
In accordance with a seventh aspect of the invention, a cordless power tool comprises a housing which includes a mechanism to couple with a removable battery pack. A removable battery pack includes a housing with one or more cells in the housing. A mechanism is in the battery pack housing coupled with the plurality of cells to equalize temperature of the plurality of cells. The mechanism may be a heat sink to equalize temperature of the cells in the housing. The heat sink may include an increased concentration of material in areas having higher temperature cells. Also, the heat sink may include a thermally conductive electrically insulating medium surrounding the cells, a base, and fins. Also, the battery pack may include apertures for dissipating heat.
In accordance with further aspects of the invention, several of the above features may be combined with one another to provide additional advantages.
Additional objects and advantages of the invention will become apparent from the detailed description of the preferred embodiment, and the appended claims and accompanying drawings, or may be learned by practice of the invention.